Problem: Simplify the following expression: $k = \dfrac{2yx + zx}{2yx} - \dfrac{5x^2 - 3zx}{2yx}$ You can assume $x,y,z \neq 0$.
Since the expressions have the same denominator we simply combine the numerators: $k = \dfrac{2yx + zx - (5x^2 - 3zx)}{2yx}$ $k = \dfrac{2yx + 4zx - 5x^2}{2yx}$ The numerator and denominator have a common factor of $x$, so we can simplify $k = \dfrac{2y + 4z - 5x}{2y}$